Mild traumatic brain injury (MTBI) also known as concussion is a major public health problem with close to 1.5 million cases a year that can result in long-term complications including Post-Concussive Syndrome and Chronic Traumatic Encephalopathy. Concerns such as these have brought MTBI to public attention. There is evidence from our group and others that even a single concussive episode can cause long-term changes in the brain that can be visualized by Magnetic Resonance Imaging (MRI). Brain iron is highly regulated and has been shown to be abnormal after traumatic brain injury in both animal and human studies. Though iron is essential for a number of normal cellular processes, it is also implicated in a number of neurodegenerative disorders as causing toxicity to the brain via the production of oxygen free radicals. Abnormal iron in the brain associated with traumatic brain injury may be a link between trauma and a host of neurodegenerative conditions which have been associated with trauma, including Chronic Traumatic Encephalopathy and Alzheimer's Disease. We propose to use MRI, including a novel technique called Magnetic Field Correlation, to quantify regional brain iron in vivo after a single concussive episode and to follow changes in brain iron over time. This application has a translational focus and we will study the relationship between brain iron and long-term changes in brain structure as well as the predictive value of brain iron in determining functional changes in the brain and clinical outcome. Identifying and understanding secondary injury such as toxicity from abnormal brain iron is a critical next step in the study of MTBI. Secondary injury cascades can potentially be slowed or stopped and, as such, are excellent potential targets for future development of therapy. The primary long-term objective of this application is to examine the role of brain iron in MTBI using MRI. If successful this work would open up avenues for potential treatment.